System of control.



N.VV.STOREH.

SYSTEM OF CONTROL.

APPLICATION FILED JUNEB, 1911 1,656,852. Patented Ma125,1913.

2 SHEETSE1HEET 1.

WITNESSES: v \gg/ENTOR tfvlzlZW/v 6425M cL/fi vc? I 4 ATTORNEY N.W."STORER. SYSTEM OF CONTROL. APPLICATION FILED JUN-E 6, 1911.

I Patented M125, 1913.

' z ennmssnnm 2.

v/W w.

- stats.

construction, and particularly adapted to 'so constructed as toembody'means for rehave'been employed in single-phase railway UNITEDSTATES PATENT. :onr cn NORMAN W. STORER, OF PITTSBURGH, PENNSYLVANIA,ASSIGNOE' TO VTESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, ACORPORATION OEZ'tP E-NNSYLVAN IA.

1 SYSTEM OF CONTROL.

Specification-of Letters Patent.

latente'd it... 25, 1913.

- Application fi 311116 6, 1911' serial 6.31585' To all whom it mayconcern:

Be it known that I, NORMAN WV. S'ronnn, a citizen of the United States,and a resident of Pittsburgh, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in'Systems ofControl, of which the following is a specification.

Myinvention relates to systems of control for electric motors and it hasspecial reference to such systems as are adapted to con-, trolsingle-phase railway motors by means of so-called liquid rheostats.

The object of my invention is to provide a systemof the above-indicatedclass which shall be simplein arrangement, effective in operation,light, durable and inexpensive in eliminate the usual multiplicity ofunit switches or contact-ore by the employment of a relatively smallnumber of liquid rheo- Anothero bject of my invention is to providesimple and adequate means for controlling the operation of liquidrheostats by means of-a continuous circulation of an electrolyte,whereby a considerable increase inheat radiation is effected whichresults in a greater uniformity of operation and materiq ally reducesthe sizes and weights of parts.

A still further object of my invention is to provide a liquid rheostatwhich shall be ducing the current to a minimum just prior to opening thecircuit in order that the are formed at the instant of interruptionshall not beso'violent as to be detrimental to the smooth'operation ofthe system or injurious to the apparatus.

In the prior art, where electric locomotives systems, the control of thedriving motors has been accomplished by means of a plurality of unitswitches and an intricatesystern of wiring, whereby'the voltage appliedto the motors has been varied in steps. Inorder not to. open the circuitbetween steps, it has also been necessary to use either resistances orpreventive coils. Furthermore, when liquid rheostats have heretoforebeen employed in connection with three-phase locomotives, theiroperation has usually been tively long periods-of time, the body ofelectrolyte was necessarily large, and elaborate provisions for coolingand heat radiation were required, thereby involving. unnec-- essaryweightcand expense.

According j to my present invention, I pro" ipose to overcome many ofthe objections and difficulties in thelprior art and to combine theadvantages of a'minimum number of switching devices and gradual speedregulau tion without the interruption of the motor current, with theadvantages of liquid rheo; stats having a" contmuous circulation ofanelectrolyte and with those of simple, light and inexpensive controlapparatus.

It is my purpose to employ comparatively few liquid rheostats, each ofwhich is to be connected to a tap on the usual transformer windingbymeans of which the voltage and speed of the motoramay be increased fromthe lowest to the highest without opening ltlle motor circuits.

It will, of course, be understood that there mal maximum rate of flow ofthe electrolyte.

Thus, it is evident that I provide a control system which embodies theoperating fea tures of a voltage control system with those of a systemof rheostat-ic control. Moreover, the electrolyte is continuouslycirculated by means of a suitable pump so that it is uniformly heatedand a free and liberal dissipation of heat is facilitated.

I shall illustrate a typical embodiment of my invention in connectionwith the control of single-phase motors, but it should be understoodthatI do not confine myself in this I I I i I vrespect, as it 1sobvious. that my invention may be employed in the control of variousother types of motors by merely making suchsimple modifications in thestructural.

details and in the arrangement of circuits and parts as mayhe, withinthe province of thoseskilled in the art.

In the accompanying drawings, Figure-1 is a diagrauunatic view of asystem of con trol, embodying my invention, Fig. 2 is a plan view of aliquid rheostat constructed in accordance with my invention, and Fig. 3is a view, partially in elevation and partially in vertical section ofthe device shown in 'Fig. .2.

Referring to the drawings in detail, the System shown comprises atransformer 1 that is adapted to receive energy from any suitablecircuit, such as a trolley conductor ,2 'anda track 3 of a railwaysystem; a 'plurality. of motors of the commutator type having armatures4 and 5 and field magnet windings 6 and 7, respectively; a plurality ofswitches 8 to 15, inclusive, for adjusting the connections of said fieldmagnet windings whereby thedirection of rotation of the motors iscontrolled; a plurality of operat-' ing magnet windings 16 forrespectively actuating said switches, a plurality of liquid rheostats17,18 and 19 for adjusting the connections of the motors with suitabletaps in the secondary winding of the transformer 1; a reservoir 20 tocontain a body of electrolyte; a pump or other suitable apparatus 21 andthe necessary piping and fittings whereby said electrolyte may becontinuously circulated through 17, 18 and 19; a plurality of valves 22,23

. and 24 for controlling the admission of electrolyte to the severalliquid rheostats; a plurality of operating magnet windings 25 forrespectively controlling the operation of the admission valves 22, 23and 24; a plurality of valves 26, 27 and 28 for controlling thedischarge of electrolyte from the several liquid rheost-ats 17, 18 and19; a plurality of actuating magnet windings 29 for respectivelycontrolling the action of the valves 26, 27- and-28; a plurality offloat valve vices 30, 31 and 32; a plurality of signal.

lamps 37 38 and 39 for respectively indicating the closure of theshort-circuiti'ng switches 33,34 and 35 a reversing switch 40 forcontrolling the operation of the magthe liquid rheostats' net windings16 of theswitches 8 to 15, in-

elusive, said reversing switch 40 comprising movable cqptact segments 41and 42 andcooperating contact terminals 43, 44 and 45.; afmastercontroller 45 for governing the circuit connections of thecontrol magnet windings, 25, 29 and 36, said master con trollercomprising stationary contact terminals 45 to 51, inclusive, and amovable con ting segment 52 that, for niotor oper ation, is adapted tocoiiperate with said stat-ionary contact terminals 45 to 51, inclugsive, upon the position-indicating lines a, b,

c, d, c and f, a series relay 53 comprising a switch member 54 and anactuating magnet-winding 55 and connected in series with the mainmotor-circuit and adapted to auto-' matically control the operation ofthe admission valves-22, 23 and 24; and a battery or other suitablesource of energy 56 for supplying energy to the control magnet windings16, 25, 29 and 36. V

The liquid rheostat's 17, 18 and 19 are of likeconstruct-ion and eachcomprises a containing tank 57 having a centrally disposed bottomdischarge opening58, an inlet port 59 located near the bottomand anoverflow port 60 disposed in the upper portion thereof. A plurality ofvertically disposed contact plates 61 are suitably secured to oppositesides of the tank 57 and project inwardly toward each other. a Anelectrode 62 is located intermediate the contact plates 61 and comprisesa supporting plate 63 and a plurality of vertically disposed contactlates 64 secured thereto and projecting out-' wardly on opposite sidesinto the spaces between thecontact plates 61.

v The electrode 62 is secured in position and insulated from the tank 57by means of suitable insulating supports 65 and the lower portions. ofeach of the plates 64 are inwardly and downwardly inclined, as shown inFig.3. A projecting portion or rod 66 of conducting material is securedto the supporting member 63 of the electrode 62 and is centrally locatedabove the discharge opening 58. Atube or sleeve 67 of insulatingmaterial surrounds the projecting portion 66 and is supported inposition above the discharge opening 58 preferably by means of a ring 68and supporting brackets 69, al-' though it may be suitably secured tothe electrode 62. The purpose of the projecting portion 66 and theinsulating tube 67 will be hereinafter set forth.

The valves 22, 23, 24, 26, 27' and 28 are of like construction and eachcomprises a movable gate member 70, a suitable casing 71 therefor and avalve seat 72. The valves 22, 23 and 24 are further provided with setnuts 73 by means ofwhich the closure of said valves may be adjusted asdesired, said valves being normally set to allow for only partialclosurein order that a slight circu- The float valve switching devices30, 31

and 32 are of like construction and each comprises a suitable balll'loat 74 secured to the free end of a lever member 75 which ispivotally supported at its opposite end in a suitable manner. A switchmember 76 is associated with the lever member 75 and is adapted tocooperate with stationary contact terminals 77 in a manner which will bereadily understood.

27 and 28, may, of course, be varied from what is herein set forth.

The construction and mode of operation of the series relay 53 is old andfamiliar to those skilled in the art andno description of the same isconsidered necessary. The relay 53 is provided, as in the usualpractice,

, with adjusting means whereby it may be set to operateat-any-predetermined current. It will be evident that if the adjustmentbe set to such a high value that the relay is never,

' of energy to the control magnet windings 16 or rarely, actuated, theoperation of the system will be entirely non-automatic,whereas, if therelay be adjusted for more moderate values, the operation of the systemwill depend upon its action as influenced by the current traversing itswinding.

Assuming the various parts of the apparatus and the circuit connectionsthereof to beias shown in the diagram and the pump 21 ,to be operating,the electrolyte in the reservoir 20 is continuously circulated throughthe partially closed admission valves 22, 23 and 24, the liquidrheostats' 17, 18 and 19, and-the discharge valves 26, 27-,apd 28,although no circuit co11nect-ions" 'IZre established. In order tooperate the driving motors, the reversing switch 40 is actuated to causeeither of its movable conducting segments 41 and 42 to make cooperativeengagement with its stationary contact ter minals it being understoodthat such engagement/of the conducting segment 41 with the contactterminals'43 and 44 insures a supply of the reversing switches 8, 13, 10and 15, while the engagement of the conductlng segment 42 with thecontact terminals 44 and 45 causes the energisw ion of the controlmagnet windings 16 of 1;. reversing switches 9, 12, 11 and 14.

For illustrative purposes, let it be assumed that the conducting segment41 is caused to-engage the c??;.::tact terminals 43 and 44 whereby theswitches 8,13, 10 and 15 are closed to establish the motor fieldconnections for forward rotation of the motors. This portion of thesystem and its operation is old and familiar to those skilled in the artand, hence, .it is not considered necessary to trace. the specificcircuit connections or to describe, in detail", the mode of operation,it being believed that no ditliculty will' be encountered inunderstanding the same. conducting segment of the master controller 45is then moved directly into con tact with the stationary contactterminals 45, 46 and 47, along the position-indicating line Z), theposition-indicating line a being passed over for a purpose to behereinafter set forth. A circuit is thus established from the positiveterminal of the battery 50, through conductor 80, conductor 81,contactterminal. 45 and conducting segment 52, where the circuitdivides, one path including contact terminal 46, conductor 83, magnetwinding 29 of valve 28, conductor 84, conductor 85 and conductor 86 tothe negative sideof the battery, and the other path including contactterminal 47, conductor 87, short circuit switch conductor 88, magnetwinding 25 of valve 24, conductor 89, conductor 90; switch 54 of theseries relay 53 and conductor 86 to the negative terminal of thebattery. Energy is thus supplied to the control magnet windings 25 and29 of the valves 24 and 28, respectively, and valve 24' is fully openedwhile the valve 28 is closed. The full normal flow of the electrolyte isthereby admitted into the liquid rheostat 19 and gradually fills thesame. As soon as the height of the electrolyte is such as to immerse thelower portions of the cooperating electrodes associated with the.rheostat 19, the main motor circuit is established from tap 91 of thesecondary winding 92 of the transformer 1, through conductor 93,electrode 62 of the rheostat 19, the body of electrolyte containedtherein, the cooperating electrode comprising the plates 61, conductor94, conductor 95, magnet winding 55 of the series relay 53 conductor90,- where the circuit. divides, one branch traversing armature 4,conductor 97, conductor 98,. switch 8, conductor 99, field n'iagnetwinding 6,- conductor 100, switch 13, conductor 101, conductor 1.02, andconductor 103 to the extremity 104 of the secondary winding 92, whilethe other branch traverses conductor 105, armature 5, conductor 106,conductor 107 switch 10, conductor 108, field magnet winding 7 conductor1'09, switch 15, conductor 110, and conductor 103 to theextremity 104 ofthe transformer winding 92? It is evident, therefore,

that a small voltage is applied to the driving motors whereby they arestarted and, operated at slow speed, depending upon the amount ofresistance in the motor circuit The provided by the immersion of theceiiperat- .ing electrodes of the liquid rheostat 19 in the electrolyte.

It should be noted that the tanks 57 and the piping of the circulatingsystem are grounded in order to prevent accidental injuries to personswho might come into con tact therewith. 7 i

As the rheostat 19 gradually becomes filled with electrolyte, resistanceis eliminatedfrom the motor circuit and gradual increases of potentialare 'applied'to the drlving motors, whey/by said motors are caused toaccelerate 1 accordance with Well known principles.

If the relay 53 be adjusted to such a value as to be operative formoderately excessive overload currents, the operation of the system 1sseml-automatic, that is, lit the motor acceleration current should, forany reason,

exceed the value for which the relay is adjusted, the switch member 54,thereof would be disengaged from its contact terminals 111.

Thus, the energizing circuit, through the of the amount of current whichtraverses the motor circuit, it is'desire'd'to reduce the-accelerationofthe driving motors or to hold the speed thereof substantially constant,the conducting segment 52 of the master con troller 15 may be moved backinto contact with the contact terminals and 46, along it theposition-indicating line a. This position of the master controller istermed the lap position, and, by such an action, the circuit previouslyestablished through the magnet winding 25 of the valve 2a isinterrupted, thereby allowing said valve to close and cut down thenormal rate of circulation of the electrolyte to its minimum value.Under these circumstances, the levelof the electrolyte is maintainedsubstantially constant,

although it, of course, rises very gradually. The effect upon theoperation of the motors is identical to that produced'by means. of theautomatic operation of the series relay 53,

and the normal operation of the system may be resumed by moving theconducting segment. 52 into contact with its cooperating stationarycontact terminals along the posltion -indicating line b.

When theelectrolyte rises within the rheostat 1-9suflicientlyto'completely immerse the coeperating electrodes, thefloat-valve switch- When. the. motor current falls.

winding 25 of the admission valve 23,

ing device 32 is actuated to complete a ciredit from the conductorthrough magnet winding 36 of the short circuiting switch 35,

lamp 39, conductor 112, switching device 32, and conductor l13toconductor 84:. Energy is thereby supplied to the magnet winding 36 ofthe short circuiting switch 35 and said switch is disengaged from itslower contact terminals 114 and makes contact with its upper contactterminals 115.

As soon as the short circuiting switch 35 is raised from its terminals114, the-energizing circuit through the magnet winding 25 of theadmission valve 2st, is interrupted and said valve is caused to assumeits partially closed position. The cooperative engagement of the movablemember of theshort circuitingswitch35 with its upper con'tact terminals115 completes a circuit from conductor'93,through conductor 116', shortcir-' cuitingswitch 35. and conductor 117 to conductor. 94, Y therebycompletely short circuiting the liquid rheostat 19 and eliminating allresistance from the motor circuit. The mo tors are, therefore, operatedeconomically on the lowest voltage tap or-the first running position. Inthe meantime, the level of the electrolyte in the rheostat 19 will'haverisen to that of the overflow port 60 and the excess 'supply thereofisdisposed ofythrough the overflow port 60 and returned to the reser- Ivoir 20. The conducting segment 52 of the master controller 4:5 may nowbe'moved into engagement with the contact terminals 48 and 49, along theposition-indicating line (Z. In this position a circuit is establishedfrom the positive terminal of the battery 56,

through conductor 80, conduetor81, contact terminal 15 and contactsegment 52, where the circuit divides, one branch including contactterminal 48, conductor '118, magnet winding 29 of the valve 27 conductor119, conductor 84, conductor 85, and conductor 86 to the negative sideofthe battery, while the other branch includes contact terminal "49,conductor 120, short-circuit switch'314,

conductor 121, magnet winding 25 or the valve 23, conductor 89,conductor 90, switch 54 of theflserics relay 53 and conductor 86 to thenegative side of the battery.

Upon the completion of the circuits iust recited, energy, is supplied tomagnet winddischargevalve 27 and magnet the closure of the former valvebeing effected ing 29 of the and the latter-valve being opened to itsfull "position.

- It should be understood that, concurrently with the establishment ofthe circuits just traced, an interruption or" the circuits throughthe-magnet winding 36 of the short circuiting switch 35, the magnetwinding of the discharge valve 28, and the magnet winding 25 of theadmission valve 2 1, is

effected. Thus, the short circuiting switch '35 is "opened, thedischarge valve 28 is lfigs. 2 andv 3 in order thatya clearunderstanding maybe had of the action which take placeduring theinterruption of the circuit by-mea'ns of the'discharge of theelecv.trolyte. For instancez As the electrolyte is v discharged from therheostat19 and its level circuit upon a falls slightly below that of theupper por-' tion of the insulating tube or 'sleeve 67, it is evidentthat thesmall body of electrolyte contained within said tube issegregated from the restof the electrolyte and, hence, a very highresistance is inserted into the circuit .just prior to the finalinterruption thereofi Furthermore, this interruption takes place betweenthe projecting portion 66 of the electrode 62 and the recedingelectrolyte, so that the are formed at the instant of break is confinedwithin the non-conducting tube 67, which prevents arcing-over from theprojecting portion 66 to the tank 57.

The insertion of this high resistance into the circuit at theinstant ofbreak cuts the current down to a minimum value and materially reducesthe violence of the arc.

Care should be exercised in determining the rate of inflow into theliquid rheostats and'the rate of discharge therefrom in order that itshall be impossible to have any two rheostats filled with electrolyte'at the same time, as this would complete a ldcal short portion of thetransformer winding 92. r The rate of discharge of the electrolyte fromany rheostat should be such that the completion offthe circuit throughthe electrodes of the adjacent rheostat shall be cffected prior to theinterruption of the circuit through the rheostat'in question. Theoperation of the system is not, however, materially affected when, inthe normal operation,

the electrodes of any two rheostats areslightly immersed at the sametime, for the reason that a considerable amount of resistance isincluded within the local circuit which limits the current therein to areason able value.

Referring again particularly to Fig. 1, having accomplished the closureof the discharge valve 27 and the opening of the ad mission valve 23, itis evident that the full rate of flow of the electrolyte is establishedinto the rheostat18 and the level of the electrolyte therein isgradually raised in contactwith the coiiperating electrodes, As soon asthe electrolyte has risen into contact with the cooperating electrodes,a circuit is. established'from a tap122 in the transformer winding 92,through conductor 123, conductor 124, electrodes 62 of rheostat 18, thebody of the electrolyte contained therein, electrode comprising plates64, conductor 125, conductor 94, conductor 95, magnet winding 55 of .4and 5 and field magnet windings 6 and 7 and conductor 103 to the extremetap 104 of the transformer winding 92. It will be noted that a completedescription of that portion of the circuit which includes the drivingmotors is not given for the reason that these circuits have hereinbeforebeen traced in detail. As the level of the electrolyte within therheostat 18'15 gradually raised, ,,resistance is eliminated and gradualincreases of potential are supplied to the driving motors whichaccelerate according to well known principles.

As already set forth, the rate of inflow into the rheostat 18 and,consequently, the rate of potential increase supplied to the motors, isdependent upon the action of the series relay 53, as will be readilyunderstood. Furthermore, these rates of inflow and of potential increasemay be manually retarded by moving the conducting segment 52 of themaster controller 45 back into contact with contact terminal 48, alongthe positionindicating linec. In this posltion the energizing circuit,through the magnet Winding 25 of the admission valve 23, is interruptedand said valve is closed, whereby a reduced rate of inflow and ofIncrease of potential is. effected, as already described iii detail.

When the rheostat 18 is filled with electrolyte, the float valveswitching device 31 is closed and a circuit is established fromconductor 118, through magnet winding 36 of the short circuiting switch34, lamp 38, conductor 126, float valve switching devite 31 andconductor 127 to conductor 84. The magnet winding 36 is therebyenergized and short circuiting switch 34 is disengaged from its lowercontact terminals 128 and brought into cotiperative engagement with itsupper contact terminals 129. As soon as the short 'circuiting switch34.1eaves its contactterminals 128, the circuit through the magnetwinding 25 of the admission valve 23 1s vinterrupted and said valve isallowed to close. Concurrently with this operation, a

circuit is completed from the conductor 123,

through conductor 130, 'short circuiting switch 34 and conductor 131, tothe conductor 94, which short circuits the rheostat 18 and eliminatesall resistance from the motor circuits, this being the second economicalvoltage tap or running position of the system.

In case a great acceleration or higher speed of the driving motors isdesired, the conducting segment 52 of the master controller 45 is movedinto contact with the contact terminals 50 and 51, along theposition-indicating line f, whereby the dis- 1 charge valve 26 is closedand the admission valve22 is opened toallow the electrolyte to graduallyfillthe liquid rheostat 17 in a mannei'. hereinbefore described.

It will. also be understoodthat as the conducting s'eg fment'52'is movedinto contact with its con-,

V tact terminals 50 and 51, the disengagement of the contact terminals48 and d9 is-etfected, whereby the short circuiting switch 34:;and thedischarge valve 27 are opened and the admission valve 23 is closed.

"As soon as the ,rheostat 17 is fillQd'With the electrolyte, the floatvalve switching device 30 is closed, thereby energizing the magnetwinding 36 of the short circuiting switch" 33 and causing said switch toassume its upper position and to short-circuit the rheo stat '17. Duringthis last operation, the

magnet Winding '25 of the admission valve 22 is deenergized and thevalve is closed,

- leaving the driving motors operating economically on the third runningposition with all of the resistance eliminated from the circuit. i v

"I have not attempted to describe in detail the circuit connectionsandthe mode of operation of the variousswitching devices i in connectionwith the employment of the -liquid rheostat l7, as they are similar to30- those-hereinbefore set forth in connection with the operation of theliquid rhe'ostats 19 and 18. Onaccount'of the previousdetaileddescription and of the similarity just referred to, it isbelieved that those skilled in the art will experience no difliculty inun derstanding the same without any further exposition there-of.

The lamps 37, 38 and 39 are preferably located near theinastercontroller and serve as signal lights to indicate to the operatorupon which rheostat the motors are operating, and the condition thereof.Evidently any other suitable indicating means may be employed for thispurpose. 45.

-Although I have shown anotdescribed a control system having specificcircuit connections and: embodying devices having more or less specificstructural details, it will be understood that various modifications maybe effected therein Without ex ceeding the spirit and scope of myinvention,

I and'I desire that only-such limitations shall to said source ofenergy.

be imposed asare. indicated in the appended claims. v

I claim as my nvention: I 1. In a control system for dynamo-electricmachines,'-the combination with asource of energy and. a plurality ofdynamo-elec trio machines adapted to receive energy therefrom, of aplurality of individually ad,

justable liquid rheostats severally connected 2;I n' a system of controlfor dynamo)- electric machines, the; combination with a source ofenergy,a plurality of liquid rheostats raving difierent voltage connections tosaid source, and a plurality of dynamo- I electric machines, of meansfor individually controlling the operation of said rheostats- Ingasystemof control for electric motors,'the combination with a source ofelectrical energy, aplurality of liquid rheostats having difi'erentvoltage connections to said source, and a plurality of electric motorsconnected in circuit with said rheostats, of means for controlling theoperation of said motors by individually controlling the operation ofsaid rh'eostats.

4:. Ina control system for dynamo-electric-machines, thecomblnationwitha source of energy, a plurality of liquid rheostats havingdifierentvoltage connections to said source, and. a plurality ofdynamo-electric machines, of means tor supplying a suitable electrolyteto said rheostats, and means for tric machines, the con'ibination with aconstant potential apparatus, a plurality of liq-' quid rheostatsseverally connected to intermediate taps in said apparatus, and a plu-.

rality of dynamo-electric machines, means 'for' successlvelyfillmg saidrheostats with said electrolyte, and means for individually controllingthe operation of said rheostats. y 7. In a control system for dynamoelectric machines, the combination with a source of energy, a pluralityof liquid rheost-ats severally connected to intermediate taps thereinand a plurality'ot' dynamo-electric machines, of means for continuouslycircu lating an electrolyte through said rheost-ats.

S. In avcont-rol system for dynamo-electrio machines, the combinationwith a constant potential apparatus, a. plurality of liquid rheostatsseverally connected to intermediate taps in said-apparatus, andaplurality of dynamo-electric machines, of a con tinuous circulation ofan electrolytethrough saidrheostats. means for causing said rheo- .statsto be filled w th electrolyte ata uni? form rate, and means forsuccessively governing the operation of said rheostats;

9. In a control system fordyna1no-electric machines, the combinationWith a constant potential apparatus, a plurality ofliquidrheostatsseverally connected to inter- "mediate tapsin saidapparatus, and a plurality of dynamo-electric machines, .of'a continuouscirculation of an'electrolyte through saidrheostats, means for causingsaid rheostats to be filled with the electrolyte at a uniform rate andmeans for varying the rate of filling. q

' 10. In a control system for dynamo-electric machines,.the combinationwith a constant' potential apparatus, a plurality of liquid rheostatsseverally connected to intermediate taps in said apparatus, and aplurality of dynamo-electric machines, of a circulating, system forefiecting a continuous flow of an electrolyte throughsaid rheostats, andmeans for causing said rheostats to be successively filled withelectrolyte.

11. In a control system for electric motors, the combination with asource of energy, a plurality. of liquid rheostats severally connectedto interinediatetaps in said source,

and a plurality of electric motors electrically associated therewith, ofmeans for successively operatingsaid rheostats to etfect gradualincreases of potential supplied to said motors.

12. Ina system of control for electric motors, the combination with asubdivided .transt'ormer winding, a plurality of liquid means forsuccessively filling said rheostats wit-h a suitable electrolyte, andmeans associated with each rheostat and dependent upon the height ofsaid electrolyte therein for short circuiting said rheostats.

14:. In a control system for electric .mqtors,

the combination with a subdivided trans former winding, a plurality ofliquid rheostats connected thereto, and a plurality of electric motors,of means for gradually filling said rheostats with a suitableelectrolyte, and means for retarding the normal rate of filling. i

15. Ina control system for electric motors, the 'combinationwith asubdivided transformer winding, a plurality of liquid rheostatsconnected thereto, and a plurality of electric motors, of means forcontinuously circulating an electrolyte through'said rheostatscand meansdependent upon the current traversing the rate'of flow.

16. In a control system for electric motors,

the combination with asupply circuit, a liquid rheostat connected Ithereto, and an electric motor adapted to receive energy therefrom, ofmeans for continuously circulating an electrolyte through said rheostat,

saidinotors for controlling means for causing said electrolyte togradually fill said rheostat, means for varying the rate of filling,andmeans dependent upon the height of said electrolyte in said rheostatfor short circuiting said rheostat when filled. v

17. In a system of control for electric motors, the combination with aconstant potential apparatus, liquid rheostats severally connected tointermediate taps therein, electric motors associated therewith, and acontinuously circulating electrolyte, of a controller for governing thesuccessive indi vidual operation of said rheostats, whereby gradualincreases of potential are supplied to said motors and for controllingtherate of said increases of potential.

18. In a control system for electric motors. the cqmbination with aplurality of liquid rheostats, a liquid-containing reservoir, means fordelivering said liquid to said rheostats, and means for returning saidliquid to said reservoir, of electro-responsive means for selectivelycontrolling the operation of said rheostats and for controlling the rateof liquid circulation.

- 19. In a control system for electric motors, the combination with aliquid-containing reservoir. a plurality of rheostat-s associatedtherewith, and means for providing a continuous circulation of liquidtherethrough, of electro-responsive means for causing said rheostats tobe separately and gradually filled with said liquid, and means fordisposing of excessiiquid when a predetermined-level is reached. i

20. In a control system for electric motors, the combination wit-h aliquid-containing reservoir, a plurality of liquid rheostats associatedtherewith, and means for providing a circulation ofsaid liquidtheret-hrough, of means associated with each rheostat for normallymaintaining a slight circulation of liquid, means for increasing saidflow to fill said rheostat, .and means for reducing-said flow when saidrheostat is filled. 21. The combination with a liquid-containingreservoir, and a plurality of tanks associated therewith, each providedwith an inletport, an outlet port and an overflow port, and means forcirculating said liquid, of electro-responsive means for. closing saidoutlet port and opening said} inlet portwhereby said tank is graduallyfilled with liquid, and automatic means for partially ClOSll g saidinlet port when the liquid reachesthe levelof said overflow port! I 22.In a control system, the combination with a source of electrical energy,a containing tank, means for discharging said liquidfrom the bottom ofsaid tank, and cooperating electrodes adapted to be immersed in saidliquid, of means for confining the final break to a. small body ofliquid.

, 23. In a control system for dynamo elecstats severally connedtedthereto, and a plu' 'rality of electric motors severallyassociatedtherewith, of means .tor circulating an-elec- 'trolyte successivelythrough said rheostats.

25. In a control system for dynamo electrio machines, the combinationWith-a derived source of energy,-a plurality of liquid rheostatsconnected thereto, a liquid-containing reservoir and means forcontinuously circulating the liquid insa'id reservoir, of means forsuccessive y directing the flow of liquid through the several rheostatsand means for preventing the filling of more than one rheoT stat at atime 26. In a control-system for dynamo electric machines, thecombination with a derived source of energy a plurality of liquidrheostats connected to taps therein, and means for circulating a liquidthrough. said rheostats, of means 'for preventing more Copies of thispatent may be obtained for source of energy, a plurality of liquid rheogtric machines, the combination with a derived source of energy, aplurality of liquid rheostats connected to taps therein, "and means forcirculating a liquid through said rheostats,of means for causing therheostats to be successively filled and means for caus: ing the liquidin 'the first rheostat to be substantially discharged prior to thefilling of said second rheostat tov prevent a local short-circuit acrosssaid derived source;

28. In a control system fordynamo electric machines, the combinationWitha. transthan one rheostat being filled atthe same time.

'27. In acontrol system for dynamo eleo former winding having aplurality of taps,

a plurality of liquid rheostats severally connected thereto and inseries circuitwith said dynamo-electric machines, and means for fillingsaid' rheostats successively with a body of liquid of means forpreventing two rhcostats from being filled at the same time. Intestimony whereof,- I have hereunto subscribed my name this 22nd day ofMay, 1911.

NORMAN WJSTORQER; \Vitnesses i i E. VVISGHMEYER, B. B. HINES.

five cents each, by addressing the Commissioner of Eaten,

- Washington. D. C

